1. Field of the Invention
This application pertains to methods and apparatus for polishing and planarization of work pieces, such as fiber optics connectors, metallographic samples, semiconductor wafers, microelectronic substrate, optical devices and the like.
2. Description of the Prior Art
The current state of the art of polishing specimens, comprising optical devices, fiber optics connectors, semiconductor wafers, micro-electronic substrate, metallographic samples, and the like largely derives from gemstone polishing machines that attempt to simulate the familiar figure eight motion which is generally recommended for hand polishing and lapping.
U.S. Pat. No. 5,667,426, which is hereby incorporated herein by reference, by Minami et al, is a method for polishing a ferrule on an optical connector by rotating an abrasive film comprised of a resin film having a layer of alumina particles disposed thereon with colloidal silicon dioxide abrasive. The film is on a rotating disk rotated by a rotating axle in a circular motion against the connector. Applying a circular motion from a rotating film has limitations. One limitation is that the linear velocity of polishing depends on the radial distance of the specimen from the center of revolution. For this reason, the method is usually applied to one circle of specimens, resulting in poor utilization of the polishing film area. Also the rotating disk lacks rigidity limiting the use of the method to dome shaped surfaces, rather than flat surfaces which require greater polishing precision.
Another rotating disk polishing machine, U.S. Pat. No. 4,979,334 by Takahashi, which is hereby incorporated herein by reference, discloses a polishing disk, supporting a polishing medium, wherein the polishing disk is made to rotate around its own axis while revolving about another axis by a rotating motor, a revolving motor and a complex mechanical mechanism. While this machine produces a better polishing effect by the combined rotating and revolving motion, the polishing disk is still a rotating disk with the drawbacks previously described for U.S. Pat. No. 5,667,426. Most of microelectronic substrate polishing and semiconductor wafer planarization incorporate those prior arts also.
U.S. Pat. Nos. 5,947,797 and 6,190,239, by Buzzetti, which are hereby incorporated herein by reference, disclose a method and polishing machine which produces a figure eight polishing pattern. The machine a polishing member mounted one of a pair of stages, wherein the pair of stages is interconnected for movement relative to each other. The polishing motion is generated by applying forces to each stage of the pair of stages to make the polishing member trace the desired path, a figure eight. The motion the stages is driven by two separate motors, one for each stage. The pattern is moved by displacing succeeding figure eight patterns by a distance. The stage moving motors are operated by an x-y controller operated by a computer. This machine is an improvement over its prior art with respect to the desirable figure eight polishing pattern and the ability to polish many pieces together. However the design is a complex one. Also the top stage extends over the bottom stage at either side of the movement. This leads to uneven stiffness across the polishing member and variations in polishing quality depending on work pieces' position. Also the displaced figure eight option to produce a moving polishing pattern is limited in its utilization of the polishing area.
The existing polishing and planarization machines either have the limitations of rotating disk machines with respect to polishing quality and radial variations, or have complex mechanisms to produce a more desirable pattern such as a figure eight polishing pattern. All existing machines require two or more motors to produce a polishing a pattern more complex than a circle and move across a polishing surface to avoid work pieces dwell on the same polishing location and causes polishing pad wore out prematurely There is a need for an improved polishing machine for producing a complex figure eight type polishing pattern while improving utilization of the polishing surface.
There is a need for a polishing machine with a simplified design wherein a complex figure eight type polishing pattern is generated using a single motor to drive a sturdy polishing platform with a simple mechanism.